Doping-Enhanced Current Rectification in Carbon Nanotube–Metal Junctions for Rectenna Applications

Using density functional theory in combination with Green's functional formalism, we study the effect of chemical doping on the electronic transport properties of carbon nanotube (CNT)-metal junctions. Both surface doping (i.e., surface fluorination) and substitutional doping with different dopant atoms (e.g., B, N, and P) are considered. Profound current rectification is obtained for the fluorinated samples, whereas substitutional doping results in only small asymmetry in the current-voltage characteristics of the system despite the smallest differential resistance. The current rectification originates from voltage-dependent charge localization in the system as revealed in our transmission spectrum analysis. We also study the effect of CNT morphology (i.e., tip opining, radius, length, chirality, and multiple walls) on the electronic transport properties of the CNT-metal junction. CNT-insulator-metal junctions are also investigated as a reference to our doped systems. The results show the possibility of creating fluorinated CNT-based diodes for practical nanoelectronic applications, such as rectenna solar cells.